This invention relates to a reciprocative sludge shovel apparatus for removal of solids from a rectangular primary sedimentation tank having a transverse trough for sludge collection or from any sedimentation tank of the type generally used in water purification and sewage treatment plants. More particularly, it relates to a sludge shovel apparatus equipped with a reciprocative trolley assembly and hoist linkage which operate together to carry a sludge shovel in a scooping position from one end of the trough across the trough bottom toward a sludge withdrawal end, to vertically lift the sludge shovel above the sedimentation level, to return the sludge shovel to its starting end and lower it for continued scooping operation. Continuous and efficient sludge removal is thereby effected with minimal disturbance of the remaining sludge during the raising and lowering of the sludge shovel.
In the sludge type treatment of sewage and industrial waste water, sludge materials such as, for example, sand and metal having a specific gravity greater than that of the liquids in which they are suspended are removed from the liquids through gravitational separation in sedimentation tanks. Many such sedimentation tanks are rectangular in plan and have a transverse trough which acts as a collection for storage of the sludge. The sludge within the trough or basin is then conveyed to another location for proper treatment. It is desirable to convey the sludge from the trough both efficiently and in a matter so as not to disturb any remaining sludge in a way which would cause it to redisperse into the liquid.
Conventional sludge removal apparatus employ sludge scraping devices to remove sludge from either the primary sedimentation tank or the collection trough. These sludge scraping devices include submerged continuous chain and flight collector mechanisms which drag sludge material up through the upper level of the liquid, submerged screw collector mechanisms which operate to remove sludge transversely across the tank or trough bottom and scrapers mounted for selected operative positioning on overhead reciprocating carriages. Each of these devices includes its own unique aspects, but each one also entails a number of drawbacks which curtail their performance and adversely affect the overall success of the waste treatment operation. For example, submerged chain and flight and screw collector mechanisms are subjected to an extremely harsh environment of corrosive water and sludge, and their frequent failure necessitates the draining of the entire sedimentation tank for repair purposes. Positionable scrapers, capable of being lifted during the return phase of their back-and-forth motion, have been complex and awkward in their operation and have not been entirely successful in avoiding the undesirable redispersion of metallic oxides and other light-weight sludge materials caused by the lifting of the scraper.